27 Before closing Our Letter, We wish to touch upon two points bearing an affinity to each other and which, because so closely connected with religious interests, have stirred up some division among Catholics - One of them is the Concordat, which for so many years has facilitated in France the harmony between the government of the Church and that of the State. On the observance of this solemn, bi-lateral compact, always faithfully kept by the Holy See, the enemies of the Catholic religion do not themselves agree. - The more violent among them desire its abolition, that the State may be entirely free to molest the Church of Jesus Christ - On the contrary, others, being more astute, wish, or rather claim to wish, the preservation of the Concordat: not because they agree that the State should fulfil toward the Church the subscribed engagements, but solely that the State may be benefited by the concessions made by the Church; as if one could, at will, separate engagements entered into from concessions obtained, when both of these things form a substantial part of one whole. For them the Concordat would amount to no more than a chain forged to fetter the liberty of the Church, that holy liberty to which she has a divine and inalienable right. Of these two opinions which will prevail? We know not. We desired to recall them only to recommend Catholics not to provoke a secession by interfering in a matter with which it is the business of the Holy See to deal.
Source: Au Milieu Des Sollicitudes (Vatican.va)